"We give that power to the audience. We basically hand the keys for the car to the audience and tell them to tell us where they want to go."

Call me a skeptic, but when I first saw the improvised scenes of "Whose Line Is It Anyway?" I had a hard time believing the performers were making it all up on the spot.

The program was my first real exposure to improvisation as a style of theatre, and likely the first for many of its audience.

"It's kind of a compliment that they think it's not made up," says improv comedian Brad Sherwood, when asked about the doubting Thomases out there. Unsurprisingly, he answered with a jest: "But at the same time they're calling us liars, so it's a bit of a double-edged sword."

Sherwood was a cast member of both the American version of "Whose Line", which aired on ABC, and the original British comedy series, which was broadcast here in the States on Comedy Central. He and fellow "Whose Line" alumnus Colin Mochrie will be presenting "An Evening with Colin and Brad" at the Hershey Theatre on June 21.

Their act, like all improv comedy routines, will be an entirely extempore creation.

"The preparation is in doing [improv] over and over again," Sherwood explains. "performing in front of a live audience. You just get good at it."

Performing without a metaphorical safety net is just the way that Sherwood and Mochrie like it. Without any other performers, or even an emcee (a role taken on by Drew Carey in the ABC series) to help crank out ideas or to save a scene, the pressure is on the duo to find what works solely from audience suggestions.

"We both love being on stage," Sherwood says, "so the beauty of it is we're both on stage the entire show. It appeals to us in that sense. Primarily the best moments in improv are between two people - you can have a third, but sometimes there's a traffic problem. We don't have a facilitator, but we give that power to the audience. We basically hand the keys for the car to the audience and tell them to tell us where they want to go."

Of course, relying on the capricious whims of a live audience can lead you to interesting places.

"We have some games where we are begging for their suggestions to be crazy," says Sherwood, "but if we're taking a suggestion for a profession, we're not looking for 'Bill Cosby riding a pogo stick.'"

Also, if you want your suggestion to be taken seriously, leave out the potty talk. (Seriously, you guys - you're not being as nearly as clever as you think.)

"We tend to not take stuff that's too filthy," Sherwood explains. "We shy away from that because of the age range for our show - seven years up to grandparents. There may be some innuendo, but we tend to shy away from the proctologist and gynecologist suggestions that we get every show. We're all about creativity, so we don't have to wallow in scatological or sexual humor."

Once the scenes get going, though, it never fails that the audience will start throwing some new and unexpected curve balls.

"I think the games that Colin and I like the most are the ones that scare us," says Sherwood. "There's one game called Fill In, where we bring people up on stage and we have the people finish our sentences for us. We're trying to get the story and tell a narrative, and we have six or seven people throwing wrenches into it the whole time."

You'd think that someone who regularly puts himself on the spot might be fearless, but there's something that gives even a veteran improviser like Brad Sherwood pause: stand-up comedy.

"I am in awe of stand-ups," he says. "More people are scared of what we do, but I'm more scared of coming up with an act and performing in front of people. It's a more adversarial thing with stand-ups, where the audience says "Come on, funny boy, make us laugh!" We invite the audience to go along on a journey with us. It's a bit more of a collaborative event. "

The midstate area has a fairly robust improv comedy scene, with several different troupes performing regularly. Sherwood's advice to them is to keep doing what they're doing.

"You have to continue to perform in front of audiences as much as possible," Sherwood says. "There's no way to find out what works and what doesn't until you're in front of an audience. It's like you're playing an instrument that doesn't make a sound until you're up on stage."